Tunisian officials say Amri’s nephew had confessed to communicating with his uncle using the encrypted app, Telegram to evade surveillance.

ISIS has claimed responsibility for the truck attack which left a dozen people dead and another 49 people wounded. A video posted to an ISIS affiliated website appears to show Amri pledging his allegiance to the terror group.

Officials have not yet determined if Amri carried out the act alone, or if he had accomplices.